1. Field of the Invention
This invention relates to a method and apparatus for removing impurities from a liquid and more particularly to such a method and apparatus in which such impurities are removed by distilling the liquid to a vapor and feeding the vapor through arrays of rotating semi-permeable screens.
2. Description of the Related Art
Thermal separation of impurities(or non-desired components) from a liquid generally involves separation of liquids with different vapor pressures or boiling points in a distillator. The upward vapor stream in the tall separation columns of the distillator is in continuous contact with the liquid phase so that efficient mass transfer occurs. The vapor stream is isolated by exposure to a condenser and the counter-current downward flowing liquid is reheated to effect vaporization at the bottom of the column by means of re-boiler. To expose the vapor stream to large surfaces of the liquid phase, a cylindrical column of plates, trays or packings are used. Distillation involves an equilibrium stage concept wherein separation is effected by the addition or withdrawal of heat. The distillation process may be isothermal(i.e. with constant temperature but changing volume and pressure) or adiabatic(i.e. with no loss of heat.
For the separation of liquids with close boiling points or systems with low relative volatilities, enhanced separation methods have been developed which rely on additional mechanisms to further modify the vapor-liquid equilibrium. These techniques may involve azeotrope distillation, pressure swing distillation, extractive distillation, salt distillation or reactive distillation. Each of these approaches relies on the addition of differing liquids or solids or an outright chemical reaction. For the separation of complex mixtures, tall separation columns are used to provide for the efficient refluxing and stripping of the liquids to yield a purified vapor which is a fraction of a given compound.
For the separation of liquids wherein the relative volatility between the components is very large, or when partial separation is only intended, a single stage flash distillation process may be used. This process could be isothermal or adiabatic. Some higher boiling components of a mixture may exhibit volatility with aqueous steam and allow for differential distillation using the steam stripping technique.
Distillation is widely practiced in the commercial separation and purification of ingredients in petroleum crudes, plant derived oils and fats, solvents, essential oils, the cleaning of natural gas, methanol, ethanol, large scale synthetic chemical compounds and other substances. In the course of distillation in columns having multiple liquid stages, the vapor passing through the liquid has a tendency for small droplets of liquid to be entrained in the ascending vapor stream. This tendency increases as the upward velocity of the vapor stream is increased. Further the vapors of many liquid compounds contain molecular aggregates that may be formed by Van der Waals forces, associations caused by quadrupole moments or inducted polarity due to the presence of double or triple bonds in the respective molecules or ionic attractions.
The system and method of the present invention provides an improvement over the aforementioned prior art distillation techniques in providing enhanced separation of impurities from liquids that do not involve variations in temperature and pressure to achieve the desired end result. Further the system and method of the present invention is capable of separating out molecular ingredients that have small boiling point differences with the desired output liquid.
In my U.S. Pat. No. 5,695,130 issued Dec. 9, 1997, a grinding system is described in which rotating screens with wide mesh openings are first used to comminute particulate material through spiral vortexes and such comminuted material is then fed to circular vortexes formed between rotating discs and stationary plates where the final grinding of the particulate material is accomplished and the final comminuted material is separated from the gas streams by centrifugal fans.
In my U.S. Pat. No. 6,044,977 issued Apr. 4, 2000, a system and method is described utilizing an array of semi-permeable rotating screens which generate vortex zones through which gas is passed to effectively remove micro particles therefrom.
The present invention is directed to the use of such rotating screens to effectively separate out impurities from a vapor stream. Further, in the present invention by utilizing screens that rotate at high speeds and generate large centrifugal gravity forces, elements of different molecular weight or geometrical configuration can be sorted out,